Recent advances in research on plasmonic enhancement of photocatalysis

The purpose of the present work is to review the results of the research on the plasmonic enhancement of photocatalytic activity of composite nanostructures consisting of metal and oxide semiconductor nanoparticles (NPs). Besides the separation of electrons and holes photoexcited in an oxide semiconductor resulting in the reduction of their recombination rate, the plasmon resonance in metal NPs deposited on or embedded into the oxide semiconductor significantly enhances the photon absorption by the nanocomposite compared with that by the single oxide semiconductor, i.e. the plasmonic enhancement. The main content of this review is a presentation of the study of various nanocomposite photocatalysts with enhanced activities due to the plasmonic enhancement effect, i.e. the plasmonic photocatalysts. Results of the study of many two-component nanocomposite plasmonic photocatalysts are presented. The simplest one consists of Au NPs or Ag NPs embedded into TiO2. The other ones consist of Au nanorods (NRs) elaborately arranged on the TiO2 surface, Au NPs deposited on different supports such as hydrotalata (HT), gamma-Al2O3, n-Al2O3, ZnO as well as TiO2 NRs, CeO2-coated bimetallic nanocomposites Au@Pd and Au@Pt, and the metal nanocrystal core@CeO2 shell nanostructure. Besides these various two-component nanocomposite photocatalysts, several three-component ones have also been studied by many authors. The results of research on Au@TiO2/Pt, Au@TiO2/Pd, Au/TiO2@Pt, Au@Pd/TiO2, Au@SiO2/TiO2, SiO2@TiO2/Au, Au/mp-TiO2/FTO, Au/mp-TiO2/ITO, Au/mp-TiO2/glass, where mp-TiO2 means mesoporous titania, as well as Ag@AgCl/CNTs, Ag@AgBr/CNTs and Ag@AgI/CNTs, are also presented. The plasmonic coupling of metallic NPs in the networks of NPs generates the complementary enhancement effect. The results of the study on the physical mechanisms of the plasmonic coupling are also included.